1. Field of the Invention
The present invention relates to a processing element used for treating a photosensitive element containing a silver halide, and particularly, to a processing element having a function to efficiently fix undeveloped silver halide remaining in a photosensitive element after development without any harmful influence and an image-forming method using the processing element.
2. Description of the Related Art
A photographic method using a silver halide is excellent in photographic characteristics such as sensitivity and gradation adjustment as compared with other photographic methods, for example electrophotography and diazo photography, and for this reason has heretofore been used in a wider scope of applications than any other photographic method. Since silver halide photography provides the highest image quality in terms of color hard copies, energetic research has been conducted in recent years.
Recently, a system has been developed in which a thermal developing process using a heat treatment substitutes for a conventional wet treatment in an image-forming treatment method for a photosensitive material containing a silver halide. An image can thereby be obtained in a simple, easy and quick manner.
In Japanese Patent Application Laid-Open (JP-A) Nos. 8-179458, 8-339065 and the like, a method is disclosed in which: a base and/or a basic precursor is mixed into a photosensitive element and/or a processing element; the photosensitive element is exposed to light; thereafter the photosensitive element and the processing element are stuck to each other; and thus stuck both elements are subjected to thermal development in the presence of a small amount of water between the elements, whereby a silver image is created on the photosensitive element.
On the other hand, in Japanese Patent Application Laid-Open (JP-A) Nos. 9-146247 and 9-204031, a method is disclosed in which: a photosensitive element having a photosensitive layer containing a silver halide, a binder, a color developing agent and a coupler on a substrate and a processing element having a treatment layer containing a basic precursor on a substrate are used; the photosensitive element is imagewise exposed to light; thereafter the photosensitive element and the processing element are stuck to each other; and thus stuck both elements are subjected to thermal development in the presence of a trace of water between the elements, whereby a high quality color image is created on the photosensitive element. In the publications, a method is also proposed in which the thus obtained image is read in a digitized form as image information and another image is created on a different record medium based on the image information.
In the above described image-forming methods, a silver image or a color image obtained on a photosensitive element is unstable since the images exist together with undeveloped silver halide. For this reason, if the silver image or the color image is observed or read on image information thereof in a digitized form after a period elapses following the developing of the images only, a deteriorated image or poor image information can be acquired.
Further, since the average density increases, if undeveloped silver halide remains on the photosensitive element, not only does it take a very long period of time to read image information on the photosensitive element in a digitized form but it is difficult to read the image information at a good S/N ratio.
In order to avoid the above described problems, a method is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 9-258402, in which a processing element having a treatment layer containing a compound with a function of dissolving developed silver and/or a silver halide is stuck to a photosensitive element after developing and then both elements are heated in the presence of a small amount of water to dissolve the undeveloped silver halide in the photosensitive element. When the silver halide is dissolved, the density of the photosensitive element decreases, so that read can be performed at a good S/N ratio. In addition, an image is stabilized, since no developing reaction occurs during storage.
A silver halide solvent employed in an example described in Japanese Patent Application Laid-Open (JP-A) No. 9-258402 is found to be problematic since a silver complex of the silver halide solvent that remains in a photosensitive element after treatment is deposited on the surface of the photosensitive element during storage following the treatment. In the publication, it is described that various kinds of silver halide solvents such as compounds that fix and stabilize silver halides, which are described in Japanese Patent Application No. 6-206331(Japanese Patent Application Laid-Open (JP-A) No. 8-69097) can be employed. The publication, however, discloses no guidelines line for selection of a compound having a specific property of swiftly diffusing from a processing element into a photosensitive element and efficiently dissolving a silver halide, wherein, as a particularly important point, a silver complex formed thereafter is not deposited on the surface of the photosensitive element.